The present invention relates to an electronic device having a communication function to be used as audio video apparatus and home use information apparatus connected to a common signal transmission line wherein operation control signals are transmitted/ received as a message.
Conventionally, as a mutual communication between audio video apparatus connected to a common signal transmission line, there is known a Domestic Digital Bus (D.sup.2 B) (IEC 84 (Secretariat) 86 I, II: Draft-Domestic Digital Bus (D.sup.2 B)). There is well known a system construction wherein audio video apparatus having a built-in communication section with a communication function are connected onto the bus as shown in FIG. 6.
When the control section (SDb-1) 13 of an electronic device B 5 shown in FIG. 6 communicates with the control section (SDa-3) 12 of an electronic device A 4, a message as shown in FIG. 7 and a communication procedure as shown in FIG. 9 have been used conventionally. In FIG. 7, a symbol S 57 represents a start bit MB 17 a mode bit, MA 58 a master address, SA 60 a slave address, CB 62 a control bit, P 59 a parity bit, A 61 a acknowledging bit, E 64 a end-of-data bit and Data data bits. FIG. 11 shows the logical structure of a logical interconnection of communication between the electronic devices B 5 and A 4. When the control section (SDb-1) 13 of the electronic device B 5 shown in FIG. 11 sends to a communication section (Db) 8 a request for communicating with the control section (SDa-3) 12 of the electronic device A 4, the communication section 8 assembles a frame A 68 as shown in FIG. 9 in accordance with the format shown in FIG. 7, and sends the frame to the electronic device A 4 via a signal transmission line 1 shown in FIG. 11. In this case, a slave status read code with a lock designation (CB field) b3b2b1b0="0010" shown in FIG. 8 is set in CB 62 of a CB frame 20 shown in FIG. 7 of the frame A 68. Upon transmission of the frame A 68 shown in FIG. 9, the communication section 8 of the electronic device B 5 knows that the destination electronic device A 4 is not communicating with another electronic device and in an unlock state. Since the communication section 8 of the electronic device B 5 has designated a lock by the transmitted frame A 68, the electronic device A 4 is caused by the electronic device B 5 to enter a lock state where the logical communication channel is occupied by the devices A 4 and B 5, when the acknowledge normal response in an acknowledging bit field (A) 61 in the CB field 20 shown in FIG. 7 is received. The connection state in this logically occupied state is shown by a primary logical communication channel 2 shown in FIG. 11. When the communication section 8 of the electronic device B 5 receives the slave status shown in FIG. 10 and provided at the communication section 7 of the electronic device A 4, in the data filed (DF) of the frame A 68 shown in FIG. 9, the communication section 8 can know on the basis of the value of bit b3 in the slave status shown in FIG. 10 whether or not the electronic device A 4 has been already locked by another electronic device. Upon reception of the frame A 68 shown in FIG. 9, the primary logical communication channel 2 shown in FIG. 11 is established and the electronic device A 4 enters a lock state occupied by the electronic device B 5. After entering the lock state, the electronic devices B 5 and A 4 communicate with each other via the primary logical communication channel 2 shown in FIG. 11 under the lock state. Lastly, the electronic device B 5 sends to the electronic device A 4 the frame C 69 shown in FIG. 9 by setting in CB 20 shown in FIG. 7 a slave status read code (CB value) b3b2b1b0="0110" with an unlock designation. The occupied state of the electronic device A4 thereby changes from the lock state to the unlock state, and thereafter the lock designation by another electronic device is allowed. Further, under the condition that the electronic devices B 5 and A 4 are communicating with each other under the lock state shown in FIG. 9, if the electronic device A 4 receives from the electronic device C 6 a frame B 70 indicating a slave status read code with a lock designation, the electronic device A 4 responds to the frame B 70 by making the bit b2 of the slave status shown in FIG. 10 in the clock state, because the electronic device A 4 has been already occupied by the electronic device B 5 and is communicating therewith.
In a conventional electronic device with a communication function or in a conventional communication method, there is established only one primary logical communication channel for mutual communication between the communication sections of different electronic devices under the logically occupied state of the primary logical communication channel Therefore, in the situation where each electronic device has a plurality of control sections which are controlled via the primary logical communication channel, i.e., in the situation where a control section of an electronic device controls one or more control sections of another electronic device via the primary logical communication channel, a control section different from the control section of the first-mentioned electronic device is allowed at the same time to control via the primary logical communication channel the one or more control sections of the other electronic device. As a result, a plurality of different control sections of the first-mentioned electronic device operates at the same time the control section of the other electronic device operates, so that it is impossible to carry out an exclusive control between control sections.
Furthermore, the operation of the control section of the other electronic device under control by the control section of the first-mentioned electronic device cannot be ensured.
Still further, a control section of an electronic device cannot carry out a broadcast communication relative to a plurality of specified control sections of another electronic device The control section of the electronic device is allowed to transmit a message only to all, or a specified one of, the control sections of the other electronic device, without the provision of a function to transmit a message to a plurality of specified control sections.
Further, if a primary logical communication channel is established between one or more control sections of a first electronic device upon request from a control section of a second electronic device, a control section of a third electronic device is not allowed at the same time to communicate with a not-occupied control section excepting the one or more control sections of the first electronic device